1. Field of the Invention
The present invention relates in general to an adjusting apparatus and a locating method. More particularly, it relates to an adjusting apparatus and a locating method for locating a lens set and image-receiving device in a optical module of an image-scanning system.
2. Description of the Related Art
FIG. 1 shows an image-scanning system, which comprises a light-radiating device 14, a image-receiving device 12, and a lens set 16. The image-receiving device 12 and the lens set 16 constitute an optical module of the image-scanning system. The light-radiating device 14 may be a cold-cathode tube having a straight line tube. For instance, the image-receiving device 12 may be a charge-coupled device (CCD).
The light-radiating device 14 moves with respect to an object 10 which is, for example, a piece of paper or a picture, along a scanning path as indicated by arrow A. The object 10 reflects the light emitted by the light-radiating device 14, as indicated by arrows B. The lens set 16 then focuses an image of the reflected light onto the image-receiving device 12 as indicated by arrow C. The image-receiving device 12 transforms the image of the reflected light (the image of the object 10) into electrical signal for further processing.
The location of the lens set 16 and the image receiving device 12 is essential to the proper functioning of the optical module. First, if the position of the lens set 16 or the image-receiving device 12 has any deviation with respect to the object 10, then the scanned image will suffer in quality. Second, if the image-receiving device 12 is not located at the required position, then the lens set 16 can not properly focus the image of the reflected light onto the image-receiving device 12, which therefore cannot receive the scanned image. Furthermore, the lens set 16 must be located at the position where the lens set 16 provides best resolution and appropriate magnification to focus the image of the reflected light onto the image-receiving device 12; if not, the image received by the image-receiving device 12 will be vague or even distorted due to the variation of the light intensity. Consequently, an adjust apparatus is always used for locating the lens set and the image-receiving device in an optical module of an image-scanning system, thereby eliminating problems such as horizontal deviation of image, received image over the boundary of the image-receiving device, and inadequate magnification and resolution for the image.
FIG. 2 illustrates an adjusting apparatus used in conventional arts. In FIG. 2, the adjusting apparatus 20 comprises three patterns 25, 27, and 21 provided in parallel and horizontally. Patterns 25 and 27 are used to calibrate the horizontal location of the image-receiving device. Two blank regions 29 are provided at two sides of the pattern 27, and used to calibrate the boundary location of the image-receiving device. The pattern 21 is used to calibrate resolution; it comprises a plurality of vertical segments 23 disposed in parallel for analyzing resolution. The adjusting apparatus 23 serves as an scanned object when carrying out location process of the lens set and the image-receiving device. The location process includes calibrating the boundary, horizontal position, and the resolution of the image-receiving device and the lens set. In practice, the adjusting apparatus must be moved corresponding to the different location procedures. For example, the adjusting apparatus is moved to a first position such that the scanning line aims at the pattern 27 when locating the boundary of the image-receiving device; and the adjusting apparatus is moved to a second position such that the scanning line aims at the pattern 21 when analyzing the resolution of the image-receiving device and the lens set. Every procedure for locating different item requires additional movement of the adjusting apparatus, therefore increasing the possibility of deviated results due to frequent movement of the adjusting apparatus. Furthermore, the conventional locating process takes a lot of time to calibrate the corresponding positions among the lens set, the image-receiving device, and the adjusting apparatus, thus increasing the time cost.
In addition, analog-to-digital converters are generally used to compensate the light saturation for different illuminations at the image-receiving device when fabricating the image-scanning system (for example a scanner). However, the illumination at the center of the image-receiving device is brighter than that at the edge of the image-receiving device, and the illumination difference will cause the scanned image at the image-receiving device to suffer from color deviation, because the linear region of the analog-to-digital converters have their limits for the compensating process. In addition, the adjusting apparatus depicted in FIG. 2 can not provide the data to analyze the ratio of the illumination at the center of the image-receiving device to that at the edge of the image-receiving device.
Therefore, a first object of the present invention is to provide a adjusting apparatus for locating the optical module (a lens set and an image-receiving device), and analyzing the illumination of the scanned image present at the center and two sides of the image-receiving device.
The second object of the present invention is to provide a locating method operating in conjunction with the adjusting apparatus which indicates the adjusting results by showing waveforms on an oscilloscope, thereby improving the accuracy and speed of location process.
To achieve the first object, the adjusting apparatus for locating a lens set and an image-receiving device provided in an optical module of an image-scanning system and analyzing illumination comprises at least the following units:
A first adjusting pattern provided at the center of the adjusting apparatus comprising at least: a white block region provided at the center of the first adjusting pattern for locating the central position of the optical module; and resolution regions provided at both sides of the white block region, for analyzing the resolution of the lens set.
Second adjusting patterns provided at both ends of the first adjusting pattern, for adjusting the boundary and horizontal location of the image-receiving device in the optical module.
Each of the second adjusting patterns comprises at least: two horizontal-deviation adjusting pattern; wherein each of the horizontal-deviation adjusting patterns comprises a first pattern for adjusting the horizontal position and deviation of the image-receiving device when disposed in the optical module, and a second pattern spaced apart from the first pattern; a boundary adjusting pattern for locating the boundary of the image-receiving device when disposed in the optical module, wherein the boundary adjusting pattern comprises the region between the first and second patterns.
The white block region is used in conjunction with the boundary adjusting patterns for detecting the illuminations projected at the center and two sides of the image-receiving device for analyzing the illumination difference between the center and two sides of the image-receiving device.
To achieve the second object, the method for locating the image-receiving device and the lens set and analyzing resolution comprises the following steps:
Provide the lens set between the adjusting apparatus and the image-receiving device such that the adjusting apparatus, the lens set, and the image-receiving device are coarsely aligned along a first direction.
Move the position of the image-receiving device, along a second direction perpendicular to the first direction, until the scanned image projected from the adjusting apparatus can be received by the image-receiving device.
Move the lens set along the first direction for coarsely adjusting the position of the lens set, until a third waveform responsive to the illumination presented at the image-receiving device has greatest amplitude at the central portion of the third waveform;
Move the image-receiving device along the second direction for coarsely adjusting the position of the image-receiving device, until the first waveform appears.
Fine adjust the position of the lens set along the first direction thereby making the central portion of the first waveform with largest amplitude.
Fine adjust the position of the image-receiving device along the second direction, until the second waveform appears, thereby achieving the location of the lens set and image-receiving device; and
Measure the amplitudes at the central portion of the second waveform and at both sides of the second waveform, thereby analyzing illumination difference.